Magazine for zigzag-folded photoconductive belt for indirect electrophotography

ABSTRACT

A magazine is provided for receiving, storing a stack of and delivering successive sections of a long endless belt of flexible photoconductive sheet material which is pre-folded in zigzag manner for use in indirect electrophotographic copying processes. Oppositely disposed upright guide walls which, in downward direction, converge inwardly to a delivery opening between their lower ends define a storage space holding a large number of the zigzag-folded belt sections stacked one upon another in upwardly bowed postures with their respective folds disposed on opposite portions of the guide walls, so that a length of the belt extending through a processing path from the ends of the stack may easily be drawn continuously from the bottom thereof and redeposited in zigzag folds onto the top thereof. Successive folds entering the top of the magazine are alternately disposed on and pressed down along the opposite guide walls. Threshold members at the delivery opening and/or resilient members bearing elastically against opposite sides of the stack aid in maintaining the folded belt sections in the required upwardly bowed postures.

United States Patent [191 Van Megen et al.

MAGAZINE FOR ZIGZAG-FOLDED PHOTOCONDUCTIVE BELT FOR INDIRECT ELECTROPIIOTOGRAPIIY Inventors: Hubertus J. Van Megen, Arcen;

Willem P. 11. A. Janssen, Blerick, both of Netherlands Sept. 4, 1973 [57] ABSTRACT A magazine is provided for receiving, storing a stack of and delivering successive sections of a long endless belt of flexible photoconductive sheet material which is prefolded in zigzag manner for use in indirect electrophotographic copying processes. Oppositely disposed upright guide walls which, in downward direction, converge inwardly to a delivery opening between their lower ends define a storage space holding a large number of the zigzag-folded belt sections stacked one upon another in upwardly bowed postures with their respective folds disposed on opposite portions of the guide walls, so that a length of the belt extending through a processing path from the ends of the stack may easily be drawn continuously from the bottom thereof and redeposited in zigzag folds onto the top thereof. Successive folds entering the top of the magazine are alternately disposed on and pressed down along the opposite guide walls. Threshold members at the delivery opening and/or resilient members bearing elastically against opposite sides of the stack aid in maintaining the folded belt sections in the required upwardly bowed postures.

10 Claims, 7 Drawing Figures MAGAZINE FOR ZIGZAGFOLDED PHOTOCONDUCTIVE BELT FOR INDIRECT ELECTROPIIOTOGRAPI-IY This invention relates to a magazine structure for receiving, storing and delivering a zigzagfolded photoconductive belt of the kind provided and utilized for indirect electrophotography according to teachings of a copending application of Martin L. van der Sterren, Ser. No. 226,413, filed Feb. 15, 1972.

According to the invention disclosed in that application, a photoconductive element is provided in the form of a very long continuous belt of flexible photo.- conductive sheet material pre-folded in zigzag manner so that the belt sections between the fold lines are disposable one upon another in a stack. This belt in endless form is then utilized for indirect electrophotography in a process and apparatus whereby the belt is moved progressively from one end of a stack composed of a large number of zigzag-folded sections thereof through a processing path and then back into the other end of the stack for a period of storage in the stack. Meanwhile, the individual belt sections are subjected successively in said path to processing steps, including imagewise exposing and image transfer steps, for the production of zerographic copies on receiving material which may be ordinary paper. It thus is made possible to use inexpensive photoconductive sheet materials for repeatedly making developable latent images of originals, even though the photoconductive substance employed in the belt material shows memory effect, and also to use highly efficient flash exposure instead of slit exposure.

The object of the present invention is to provide a magazine structure which is especially useful for continuously and reliably receiving, storing a stack of and delivering successive sections of the zigzag-folded photoconductive belt in endless form.

According to this invention, a magazine is provided which comprises two oppositely disposed upright guide structures defining between them a space for storing a stack composed of a large number of sections of the zigzag-folded belt disposed one upon another, with an opening at the bottom of said structures for delivery of the belt, together with means engaging a portion of the belt extending through that opening for propelling the belt from the lower end of the stack and means engaging a portion of the belt at the top of said structures for feeding the belt onto the stack. The guide structures are spaced apart at an upper level of said space by a distance less than the length of each of the sections of the belt between successive folds thereof, and they converge each toward the other from that level downward to the level of the delivery opening, so that the successive sections of the belt may be stacked in said space in upwardly bowed postures with their respective folds disposed on opposite portions of the guide structures and will be increasingly bowed upwardly as their respective folds progress downwardly on the guide structures.

Thus, the curvature of the belt sections increases as they sink lower in the magazine and, due to the differences in curvature, the many belt sections in the stack do not press heavily on each other. Especially the portions of the stacked sections near their folds gradually become separated further from each other, and some elasticity in the belt material near the folds often causes them to open slightly so as to increase the degrees of separation. This enables the lowermost belt section of the stack to be removed continually from the magazine with a limited force and with little friction, for the stack nowhere rests heavily on that belt section which is always the one being fed from the magazine. As the lowermost belt section is transported out of the magazine, the folds of sections stacked above it slide downwardly on the guide structures to the level of the delivery opening, thus giving greater bowing to and greater support from those belt sections, so that the contact, little as it is, already existing between the lowermost belt section and the section lying immediately above it is further decreased immediately at the beginning of delivery of the former.

In a preferred embodiment of the magazine, the guide structures may be formed with inner surfaces which are approximately straight at and above the upper level where the top of the stack is located, but which in downward direction are smoothly curved inwardly toward the center line of the space occupied by the stack and are provided with a greater inward curvature at their lower ends than at any higher level. The lower ends of these structures in the vicinity of the delivery opening may extend almost horizontally towards each other.

As a further feature of the magazine structure, means are provided for positioning successive folds of the belt downwardly along opposite portions of the guide structures as these folds are deposited in the space containing the stack, so that each belt section between two successive folds will be layed in upwardly curved posture upon a stack of the belt sections bowed upwardly in said space. suitable positioning means comprise two substantially horizontal rail members, such as rollers or rods, each of which is movable up and down along the inside of one of the guide structures, and means operable in correlation with the feeding of the belt into the magazine for alternately moving one of the rail members downwardly, so as to press down along one of the guide structures a fold of the belt just deposited in the magazine, while moving the other of the rail members upwardly to a position above the next fold of the belt as the latter is being deposited.

The desired upwardly bowed postures of the belt sections in the magazine may be further assured with the aid of means which will arrest downward movement of the folds of the lowermost section at a desired delivery location, or of means which will retard downward movement of portions of the stacked belt sections between the respective folds thereof.

According to the first and preferable of these expedients, arresting means are provided in the form of threshold members on the lower ends of the guide structures adjacent to the delivery opening, these members presenting upwardly extending surfaces to arrest the folds of the lowermost section of the belt material in the magazine at a location thereof in which the lower stacked sections will be kept bowed upwardly in a highly arched form.

According to the second of the ways mentioned,

means are provided at a location or locations between the guide structures to engage and retard downward movement of portions of the stacked belt sections between their respective folds, such as their opposite side edges extending perpendicularly to the folds. These means support to a considerable degree the weight of the stack near the middle of it and aid the bowing of the stacked sections, thus keeping them from bearing heavily on the lowermost belt section of the stack when it is in position to be fed from the magazine. Such means may be provided in the form of resilient members, preferably brushes having resilient bristles, arranged to bear against and elastically exert friction upon the opposite side edges of the stacked belt sections.

In some circumstances a combination of both of the described means may be advantageous.

The foregoing and other objects, features and advantages of the invention will be further apparent from the following detailed description and the accompanying drawings of illustrative embodiments thereof. In the drawings:

FIGS. la, lb and 1c are schematic views in side elevation, cross-section and perspective, of portions ofa zigzag folded photoconductive belt which is to be stacked in and delivered from and back to the magazine according to the invention;

FIG. 2 is a schematic vertical transverse cross-section through one embodiment of a magazine holding a stack composed of many superposed sections of the belt;

FIG. 3 is a similar section of a modified embodiment of such a magazine;

FIG. 4 is a similar section of a third embodiment of such a magazine; and

FIG. 5 is a schematic vertical longitudinal section through approximately the middle of the stack and the brushes shown in FIG. 4.

The zigzag-folded belt in the form shown is composed of a photoconductive sheet material which, as shown in FIG. lb, comprises a support 3a and a photoconductive layer 3b. As indicated in FIG. 10, further markings 3c are applied to the belt adjacent to alternate folds thereof to facilitate detection of the location of its fold lines by optical scanning means.

The support 3a of the belt may be a band of any material that can be folded, retain the fold and withstand frequent unfolding and refolding. Paper, synthetic paper and plastics may be used as the support material, but paper is preferable.

The photoconductive layer 3b is coated on the support and preferably is a layer of a finely divided photoconductor dispersed in a binder. Any known photoconductive substance, inorganic or organic, may be used as the photoconductor. Selenium, zinc oxide, cadmium sulphide and poly-N-vinylcarbazole are examples of effective photoconductors. For a detailed specification of suitable photoconductors reference is made to pages 165 and 170 of Dessauer and Clark, Xerograph and Related Processes" (The Focal Press, London and New York, 1965). The photoconductor is dispersed in an insulating, film-forming binder which is selected so that the layer formed will be flexible. Organic or inorganic binders (e.g., glass binders, silicones or thermoplastics) may be used. Suitable binders are specified on page 165 of Dessauer and Clark. In order to extend the lightsensitivity of the layer to a greater part of the spectrum, dye sensitizers may be added to the layer. Examples of such sensitizers are: Acridine Orange, fluorescein, eosine, Rose Bengal, methylene blue, Rhodamine B, and others noted on page 136 of Dessauer and Clark.

According to a preferred practice, the photoconductive layer 3b of the belt material is made of zinc oxide dispersed in a binder which is a mixture of polyvinyl acetate and an acrylic resin to which an activator and a sensitizer have been added.

The photoconductive belt, made for example as along continuous band of a paper or a plastic composition coated with a photoconductive layer, is pre-folded in zigzag manner, as indicated schematically in FIG. la, so that the successive sections thereof between the fold lines are disposable one upon another in a stack. The length and width of each section between two successive folds are made slightly greater than the size of the largest copies required to be produced in the use of the belt. If such copies are of A4 size (210 mm X 297 mm), the sections are given a size of approximately 250 mm by 350 mm.

While the belt can be given any length desired, a practical length is one of between 200 and 500 meters. If destined for making copies of A4 size, a belt of that length contains approximately 500 to 1,500 sections. Therefore, assuming that the photoconductive layer can be used for only about 300 times before the belt should be replaced, about 100,000 to 450,000 copies may be made by use of the one belt.

In a folded up form, with its many sections between the zigzag folds disposed one upon another, the belt forms a compact stack, or package, which is easy to handle. The belt in this form is mounted in the magazine shown in FIG. 2, FIG. 3 or FIG. 4, which constitutes a part of a copying apparatus, and a free end portion of the belt is threaded through the copying apparatus so as to dispose a length of the belt in a path extending from the lower end of the stack through the processing stations of the apparatus and thence back into the magazine to the upper end of the stack. When the belt has been so threaded for use, its free ends are joined together, e.g., by means of an adhesive tape having sufficient mechanical properties and folding endurance, thus making it into an endless belt.

Referring now to particulars of preferred forms of the magazine, FIG. 2 shows a magazine formed principally by two oppositely disposed upright guide structures, or walls, 1 and 2 which define therebetween a space for storing a stack composed of a large number of zigzag folded sections of the belt 3 disposed one upon another. These guide structures are spaced apart at an upper level of said space by a distance less than the length of each section of the belt, and they converge each toward the other in downward direction to the level of a delivery opening definedbetween their lower ends. They have smooth inner surfaces which in the vicinity of said upper level may be almost straight but which, as they progress downward, are smoothly curved inward toward the center line of said space and are provided with greater inward curvature, or a smaller radius thereof, at their lower ends than at any higher level.

The folds pre-formed in the belt 3 tend when the belt is slack to bring it into a zigzag-folded condition but are sufficiently elastic that they will flatten out in the path of the belt between conveyor rollers. Folds of the uppermost and lowermost sections in the magazine are indicated schematically at 19 in FIG. 2. In this figure the belt is propelled between driven feed rollers 4 and 5 so as to be deposited slack onto the top of the stack in the magazine. A portion of the belt extending through the delivery opening from the lower end of the stack is propelled out of the magazine by two driven rollers 12 and I3 situated below the center of the delivery opening. At the opposite side edges of the stack formed in the magazine there are upright guides 11 which confine the belt material laterally to the desired location but normally need not come into contact with the material.

At each side of the magazine there is also a rockable arm which is pivoted on a frame member near to one of the guides 11. The ends of the arms 10 extend beneath protruding ends of substantially horizontal rail members 6 and 7 which are disposed at the inner surfaces of the guide walls 1 and 2 and are movable up and down along the upper regions of these surfaces in paths limited by end guides 8 and 9, respectively. The rail members shown have the form of round rods, or rollers.

As the belt 3 is deposited from the feed rollers 4, 5 into the magazine, the arms 10 are rocked synchronously by any suitable motor device so that their ends oscillate between the position shown in FIG. 2 and a position in which the right-hand end of each arm is raised as high as the left-hand end seen in FIG. 2. In the illustrated position of the arms 10 their lowered right hand ends have let the rail member 7 rest upon and press down along the inside of wall 2 a fold of the belt previously deposited against that guide structure, and the second following fold 19 of the belt is being deposited to the same side of the magazine.

The rocking of the arms now moves their left-hand ends downward, thus placing the rail member 6 upon the fold last previously deposited against the inside of wall 1 so as to press that fold downward, while the right-hand ends of the arms are moved upward so as to lift member 7 to and past the location of the incoming fold. The rising rail member 7 easily traverses the fold 19 then being deposited, thus reaching an elevated position above it so that, in the next half-cycle of the arm movements, member 7 will move down into that fold 19 and press down upon the folds of the belt section already stacked in the magazine.

It results that each incoming belt section between two successive folds of the belt has its folds positioned downwardly along opposite portions of the guide structures 1 and 2 so that it is layed in upwardly curved posture upon a stack of sections of the belt previously bowed upwardly in the belt storage space of the magazme.

The guide structures 1 and 2 as shown in FIG. 2 are provided with means on their lower ends for arresting downward movement, at the level of the delivery opening, of the folds of the lowermost belt section in the stack. These means comprise threshold members 14 and 15, formed as curved extensions of said lower ends, which present upwardly extending surfaces to arrest those folds, until they are drawn out of the magazine, at a location thereof in which the belt section between them is bowed upwardly in a highly arched posture. The threshold members merge into the walls 1 and 2 via relatively sharply curved valleys at 16 and 17.

The upwardly bowed postures given to the belt sections stacked in the magazine are such that they in effect appear to stand on their respective folds disposed on opposite portions of the guide structures 1 and 2, with the folds of the lowest belt section situated in the valleys l6 and 17. The guide structures themselves converge in downward direction along inwardly curved planes that roughly follow the contours to which the folds of the stacked belt sections tend to adapt themselves, while the folds of the lowest sections of the stack are pressed somewhat farther inwards than accords with their natural posture.

Consequently, only a very small part of the weight of the stack is borne by the belt sections located at the bottom of the stack in position to be drawn through the delivery opening, and there is little frictional resistance to the delivery of the stored sections of the belt from the magazine for movement again through the processing stations of the copying apparatus. When the foldengaging surfaces of the magazine are made very smooth, for example, by chromium-plating them or lining them with Teflon, plush, or the like, the total frictional resistance to sliding of the belt sections down along the guide structures and over the threshold members is very slight indeed.

FIG. 2 shows a fold 19 of the lowest stacked section of the belt being drawn out of the left-hand side of the magazine. It is evident that, once this belt section becomes released at that side, it has hardly any further contact with other belt material in the magazine; at no moment will it slide appreciably against or relative to the adjacent belt section of the stack. Thus, there is considerably less friction than in any other known vertical stacking system.

With regard to the driving of the tilting arms 10, it is satisfactory in many cases to rock them in correct correlation with the deposition of folds of the belt into the magazine by means of solenoids energized at the proper moments via a photocell arrangement responsive to markings on or immediately adjacent to the folds of the belt. It may be easier, however, to have the synchronous movement of the arms 10 effected by a mechanical connection with the drive for the belt propelling means, such as rollers 4 and 5. These and other ways of driving the arms will be obvious to mechanical engineers.

If the belt material is naturally rather limp or tends to become limp, for instance due to atmospheric moisture, it may occur that the lower belt sections of the stack will not retain the desirable arched posture indicated in the drawings but will tend to sag inwards as indicated by a broken line 18 at the right-hand side of FIG. 2.

For such a condition, a modification of the magazine as indicated in FIG. 3 is to be preferred. According to this modification, the threshold members 14 and 15 are hinged at 20 and 21, respectively, to the lower ends of the related guide structures, and drive means (not shown) are provided for moving these members in opposite phase so that when one of them is in a belt delivery position (that of member 14 as indicated in FIG. 3),

in which-its upwardly extending or fold-arresting surface lies approximately normal to the lower end portion of the related guide structure, the other of them will be in a stack-supporting position (that of member 15 in FIG. 3) in which its said surface lies at an acute angle to the related guide structure in order to hold the material of the lowest belt section in its correct position. In this modification the threshold members 14 and 15 are oscillated in the same frequency as the arms 10, so that a simple mechanical coupling between the drives for these parts can be used. The movements are so effected, however, that each threshold member remains in its stack-supporting position as long as practicable and is disposed in its belt delivery position for as little time as practicable, i.e., only during removal from the magazine of the fold of the belt which lies next to that member.

For limp belt material it is also advantageous to arrange the feed rollers 4 and in such a way that they can be changed in position in correlation with the movement of folds into the magazine space so as to feed portions of the belt material adjacent to each fold thereof toward the guide structure against which that fold is to be disposed in the magazine. For this purpose, the roller 5 may be mounted in a fixed position and the roller 4 may be displaced about the axis of roller 5 between the position 4 shown in full lines and the position 4' shown in broken lines in FIG. 3. A broken line leading from an arrow to wall 1 indicates the direction of feeding of the belt material, toward that wall, which exists in position 4' of the feed rollers.

FIGS. 4 and 5 show a further modification of the magazine system. Here the guide structures 1 and 2 in downward direction curve inwardly into almost horizontal end portions 22 and 23 having no threshold members such as those shown in FIG. 2 or FIG. 3. Brushes 24 and 25 having elastic bristles are mounted along the opposite side edges of the stack. There may be one brush on each side at the middle of the magazine space, as shown in full lines in FIG. 4, or two brushes may be provided on each side in symmetrical relation to the middle as indicated by broken lines at 24' in FIG. 4. The bristles of the brushes may be of rubber or of a flexible plastic material.

As shown in FIG. 5, the brushes may be placed obliquely so that their bristles will bear against side edges of the belt sections in the stack with greater force at the lower sections of the stack than at the upper sections thereof. Alternatively, the base of each brush may be placed vertically, in which case the bristles may increase in length in downward direction so that they will exert greater force, or gripping and motion retarding action, upon edges of the lower sections of the stack than edges of the upper belt sections. This latter dispo sition, which is often preferred, is indicated in broken lines at the left-hand side of FIG. 5. In some cases it is advisable to construct and mount the brushes so that they do not bear against several of the lowest belt sections in the magazine but end at a slightly higher level than that shown in FIGS. 4 and 5.

Instead of brushes, other resilient members may be used for elastically exerting friction on the opposite side edges of the stacked belt sections and thus aiding them to retain the required upwardly bowed postures in the magazine. Elastic pads, for instance of foam rubber, may be so used. Brushes, however, have definite advantages, notably when the opposite side edges of the stacked belt sections are not always lying exactly in line with each other.

The guide walls 1 and 2 in the modification of FIGS. 4 and 5 preferably have only a slightly more pronounced inward curvature than would the planes defined by the loci of the folds of the stacked belt sections if those walls were not present. The walls slightly support the folds and press them inwards, but the support they give to the folds is of smaller degree than in the embodiments of FIG. 2 and FIG. 3, where the guide walls press the folds slightly more inward and so deviate slightly more from the curved planes which would be defined by the loci of the folds if there were no guide walls. Thus, according to FIGS. 4 and 5, the stack seems to hang between the brushes and is only slightly supported by the guide walls; so it takes a configuration as indicated in FIG. 4, whereby portions of the belt adjacent to the folds tend to become further separated from one another as they progress downward in the magazine. This facilitates smooth delivery of the belt from the magazine.

We claim:

1. A magazine for receiving, storing and delivering portions of a continuous belt of flexible photoconductive sheet material pre-folded in zigzag manner so that the successive sections thereof between the folds thereof are stackable one upon another, comprising two oppositely disposed upright guide structures defining therebetween a space for storing a stack composed of a large number of said sections disposed one upon another; an opening at the bottom of said structures for delivery of said belt; means for propelling said belt through said opening from the lower end of said stack; and means engaging a portion of said belt at the top of said structures for depositing said belt onto said stack; said guide structures being spaced apart at an upper level of said space by a distance less than a length of each said section and having respective, oppositely disposed inner surfaces converging each toward the other, with each of said surfaces curved smoothly inwardly toward the center line of said space, from said upper level downward to lower end portions of said surfaces at the level of said delivery opening, so that said sections may be stacked in said space in upwardly bowed postures with their respective folds disposed on opposite portions of said inner surfaces and will be increasingly bowed upwardly as their respective folds progress downwardly on said surfaces.

2. A magazine according to claim 1, said inner surfaces having greater inward curvature at their lower end portions than at any higher level.

3. A magazine according to claim 1, further comprising means for positioning successive folds of said belt downwardly along opposite portions of said inner surfaces as the folds are deposited in said space, so that each belt section between two successive folds will be layed in upwardly curved posture upon a stack of said sections bowed upwardly in said space.

4. A magazine according to claim 3, said positioning means comprising a rail member movable up and down along the inside of each of said guide structure and means operable in synchronism with said belt depositing means for alternately moving one of said rail members downwardly to press down along one of said structures a fold of saidbelt just deposited in said space while moving the other of said rail members upwardly to a position above the next fold of said belt as the latter is being deposited in said space.

5. A magazine according to claim 1, said guide structures having on their respective lower ends and bordering said delivery opening threshold members each of which presents a curved surface extending upwardly from the lower end of said inner surface of the related guide structure to arrest a fold of the lowermost of said stacked sections.

6. A magazine according to claim 5, said threshold members each being hinged for movement from a belt delivery position in which its said surface lies approximately normal to the lower end portion of said inner surface of the related guide structure to a stacksupporting position in which its said surface lies at an acute angle thereto.

7. A magazine according to claim 6, and means for moving said threshold members in opposite phase between said positions thereof in correlation with delivery of said belt from said stack, so that the one of said members over which a fold of the belt is being pulled from said space will be in its belt delivery position while the other of said members is in its stack-supporting position.

8. A magazine according to claim 1, further comprising resilient members bearing against and elastically exerting friction on the opposite side edges of said stacked sections for retarding downward movement of portions of said stacked sections between the respective folds thereof so as to support such sections in upwardly bowed postures, said resilient members bearing against such side edges with greater force at the lower sections of the stack than at the upper sections thereof.

9. A magazine according to claim 1, further comprising brushes mounted between said guide structures and respectively having bristles bearing elastically against the opposite side edges of said stacked sections for retarding downward movement of portions of said stacked sections between the respective folds thereof so as to support such sections in upwardly bowed postures.

10. A magazine according to claim 9, said brushes being mounted so that their respective bristles are substantially parallel to each other, said bristles increasing in length from the top towards the bottom of said brushes so that they exert greater force on edges of the lower sections of the stack than on edges of the top sections thereof. 

1. A magazine for receiving, storing and delivering portions of a continuous belt of flexible photoconductive sheet material prefolded in zigzag manner so that the successive sections thereof between the folds thereof are stackable one upon another, comprising two oppositely disposed upright guide structures defining therebetween a space for storing a stack composed of a large number of said sections disposed one upon another; an opening at the bottom of said structures for delivery of said belt; means for propelling said belt through said opening from the lower end of said stack; and means engaging a portion of said belt at the top of said structures for depositing said belt onto said stack; said guide structures being spaced apart at an upper level of said space by a distance less than a length of each said section and having respective, oppositely disposed inner surfaces converging each toward the other, with each of said surfaces curved smoothly inwardly toward the center line of said space, from said upper level downward to lower end portions of said surfaces at the level of said delivery opening, so that said sections may be stacked in said space in upwardly bowed postures with their respective folds disposed on opposite portions of said inner surfaces and will be increasingly bowed upwardly as their respective folds progress downwardly on said surfaces.
 2. A magazine according to claim 1, said inner surfaces having greater inward curvature at their lower end portions than at any higher level.
 3. A magazine according to claim 1, further comprising means for positioning successive folds of said belt downwardly along opposite portions oF said inner surfaces as the folds are deposited in said space, so that each belt section between two successive folds will be layed in upwardly curved posture upon a stack of said sections bowed upwardly in said space.
 4. A magazine according to claim 3, said positioning means comprising a rail member movable up and down along the inside of each of said guide structure and means operable in synchronism with said belt depositing means for alternately moving one of said rail members downwardly to press down along one of said structures a fold of said belt just deposited in said space while moving the other of said rail members upwardly to a position above the next fold of said belt as the latter is being deposited in said space.
 5. A magazine according to claim 1, said guide structures having on their respective lower ends and bordering said delivery opening threshold members each of which presents a curved surface extending upwardly from the lower end of said inner surface of the related guide structure to arrest a fold of the lowermost of said stacked sections.
 6. A magazine according to claim 5, said threshold members each being hinged for movement from a belt delivery position in which its said surface lies approximately normal to the lower end portion of said inner surface of the related guide structure to a stack-supporting position in which its said surface lies at an acute angle thereto.
 7. A magazine according to claim 6, and means for moving said threshold members in opposite phase between said positions thereof in correlation with delivery of said belt from said stack, so that the one of said members over which a fold of the belt is being pulled from said space will be in its belt delivery position while the other of said members is in its stack-supporting position.
 8. A magazine according to claim 1, further comprising resilient members bearing against and elastically exerting friction on the opposite side edges of said stacked sections for retarding downward movement of portions of said stacked sections between the respective folds thereof so as to support such sections in upwardly bowed postures, said resilient members bearing against such side edges with greater force at the lower sections of the stack than at the upper sections thereof.
 9. A magazine according to claim 1, further comprising brushes mounted between said guide structures and respectively having bristles bearing elastically against the opposite side edges of said stacked sections for retarding downward movement of portions of said stacked sections between the respective folds thereof so as to support such sections in upwardly bowed postures.
 10. A magazine according to claim 9, said brushes being mounted so that their respective bristles are substantially parallel to each other, said bristles increasing in length from the top towards the bottom of said brushes so that they exert greater force on edges of the lower sections of the stack than on edges of the top sections thereof. 